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Old 27-03-2017, 03:59   #1
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Wet Glass Blasting through years of bottom paint

I am midway through having my hull bottom blasted right now to remove years of basecoat + antifoul paints on a 40' monohull

Motivation: flaking, wide range of crumbling down to all different layers including the thin red gelcoat topper
Surveyor recommended stripping to gelcoat and brining back up with 2 basecoats and 2 AF coats

As an ex-charter boat, it's layers are like a gobstopper:
Gel coat
Super thin red paint - well bonded to gel
Grey base
Blue AF
More grey base
More blue
Strange green gloss plasticky coat in parts
More blue

I tried scraping, some came off thick and fast, some stuck way better and progress was not quick enough

I tried Interlux 299e fibreglass friendly stripper. I think I join the disappointed side of users, with too much paint layers for it to be able to assist

I waved white flag and consulted blasters.
Paint is coming off good now, but I am at the other end of the spectrum.

I am now concerned that it's taking too much off of the boat

I have found spots where it has been blasted for too long and gone past white and found fibreglass
(Worst case at this point is not knowing how thin the fibre could/would get before being a risky weak spot)

Questions:
How do I cover up the gelcoat-less spots?
Would a roughed up gelcoat layer be a good blank canvas to paint directly on to with base coat paint?
I've heard and seen mention of "fairing" but don't fully understand the technique, or when to apply it - do I have to prep/prime the roughened gelcoat before painting on the first coat of "Interlux Interprotect 2000 base"?
I do get that topside repairs and detailing want to be done with extra care to ensure a good appearance and finish - is bottom painting and prep simpler? To achieve solid protection instead of aesthetics?

Can of worms currently open - want to close and seal it safely, rather than saran-wrap it and naively drop it into the water
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Old 27-03-2017, 04:21   #2
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Re: Wet Glass Blasting through years of bottom paint

I'm going to guess that the grey that you and see and the strange green in the layers of paint are actually barrier coat. That said, I think you've made the right choice to take it all off and start from scratch. You'll know what you have on there and it will be easier to maintain.

If the blaster is blowing through the gel at some points it's not the end of the world. I don't think you need to worry about the thickness of the glass...I'm assuming that as soon as the blaster sees that he's through the gelcoat, he stops, whispers "oops" to himself, and moves on. So he just took off the gelcoat, which was probably thin. If you build up enough barrier on top of it, you'll be fine.

If it were me I would plan on putting four or more coats of barrier coat on the entire hull below the waterline when the blasting is done. Yes, right over the exposed fiberglass. Up to ten coats would not be too many. Put on one coat and let it cure, and then you'll be able to see every flaw in the surface. Fairing is the process of making the surface smooth, and the term can be applied to small areas, where you have gouges and scratches, or much broader areas where due to deformation or damage the hull is not it's proper shape. You're probably looking at the first category, almost exclusively I'm going to guess. After the first coat of barrier you fill those areas that are obvious flaws with the filler of your choice, and sand fair. You'll also want to surface scuff all of the barrier for good adhesion of the next coat. Put on the next coat. If you determine that there is no more fairing to do, you can hotcoat the subsequent coats, which means applying them before the previous coat has fully hardened, resulting in a chemical bond that is stronger and more durable than just a mechanical one. Then on goes the AF.

The two main concerns with bottom work are 1) preventing water from penetrating into the glass, and 2) getting good adhesion of all the layers. So prep is very important...adequate sanding, adequate cleaning. Also paying attention the the requirements of the coatings you are using in terms of specified time between coats, temperature, etc.

The last thing you want is doing all this work and having the paint start to fail. That's what you're seeing with the old flaking, alligatored paint. That did not have to happen and it did not have to get that way. That's the result of lazy ownership over the years, just slapping on coats of paint over and over again without maintaining it.

There's obviously a lot more involved, and different approaches to the basic process, so you have more research to do and opinions to solicit.
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Old 27-03-2017, 04:42   #3
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Re: Wet Glass Blasting through years of bottom paint

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Old 27-03-2017, 05:15   #4
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Re: Wet Glass Blasting through years of bottom paint

Looks to me like someone layered barrier on top of existing bottom paint at one point, but hard to tell.

Don't worry about the burn through spots. Just sand the obviously proud areas (looks like someone used epoxy thickened with a structural instead of fairing filler) and fill the obvious gouges, nicks, and other flaws. Sand the whole hull to knock off the roughness of the blasting, and wash and wipe it down with a good solvent. After you put the first coat of barrier on, any other smaller or less obvious flaws will leap out at you and you can go back and fix those.

Some barrier coat is thicker, and some is thinner. The advantage after blasting of using a thicker barrier is that it will level out the roughness and fill some smaller flaws.

If you're doing four or more barrier coats, you may also want to sand before the final coat. Orange peel builds up to a point that can make future maintenance more difficult. The more time you invest in getting the barrier coat relatively smooth and clean now the better. It's the foundation for your bottom and you don't want to be fighting it in years to come as you maintain the bottom.
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Old 27-03-2017, 05:26   #5
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Re: Wet Glass Blasting through years of bottom paint

Go Online and look at a Osborne Brush. Ten years ago I decided to strip the bottom of our previous boat to complete a barrier coat project. There I was hand sanding the hull thinking this was going to take forever. A great friend who built custom log homes for a living who also owned a Niagara watched me start the task. He came back a few hours later and I think I had cleared about a square foot of paint off the hull. Bill he says..here try this. He handed me a Makita variable speed grinder with a brush head on it that looked liked Medusa,s hairdo. He explained to me that it was the tool he uses to polish the logs after assembly to make them smooth and he had used it on his boat. Using it at a slow rotation I was able to remove all the bottom paint on a Tanzer 8.5 hull in 6 hours. The biggest effort was holding on to the power tool for long periods of time. It really did work without any damage to the glass structure or surface. We had our surveyor update our records to reflect the condition of the hull PRIOR to 6 coats of epoxy being applied. Pictures were taken, the current owner knows what he got. A very easy way to take charge of a difficult task. Mask, gloves,etc not an option.
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Old 27-03-2017, 08:34   #6
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Re: Wet Glass Blasting through years of bottom paint

Quote:
Originally Posted by WoodFamSkipper View Post
I am midway through having my hull bottom blasted right now to remove years of basecoat + antifoul paints on a 40' monohull

Motivation: flaking, wide range of crumbling down to all different layers including the thin red gelcoat topper
Surveyor recommended stripping to gelcoat and brining back up with 2 basecoats and 2 AF coats

As an ex-charter boat, it's layers are like a gobstopper:
Gel coat
Super thin red paint - well bonded to gel
Grey base
Blue AF
More grey base
More blue
Strange green gloss plasticky coat in parts
More blue

I tried scraping, some came off thick and fast, some stuck way better and progress was not quick enough

I tried Interlux 299e fibreglass friendly stripper. I think I join the disappointed side of users, with too much paint layers for it to be able to assist

I waved white flag and consulted blasters.
Paint is coming off good now, but I am at the other end of the spectrum.

I am now concerned that it's taking too much off of the boat

I have found spots where it has been blasted for too long and gone past white and found fibreglass
(Worst case at this point is not knowing how thin the fibre could/would get before being a risky weak spot)

Questions:
How do I cover up the gelcoat-less spots?
Would a roughed up gelcoat layer be a good blank canvas to paint directly on to with base coat paint?
I've heard and seen mention of "fairing" but don't fully understand the technique, or when to apply it - do I have to prep/prime the roughened gelcoat before painting on the first coat of "Interlux Interprotect 2000 base"?
I do get that topside repairs and detailing want to be done with extra care to ensure a good appearance and finish - is bottom painting and prep simpler? To achieve solid protection instead of aesthetics?

Can of worms currently open - want to close and seal it safely, rather than saran-wrap it and naively drop it into the water
I'm not sure of where you are located, but in Central Florida there is a company called Bottom Savers. He uses a patented type of planing tool to remove paint, epoxy, barrier coat, even gel coat. He can stay within about .003" tolerance. He took my boat bottom down to gel coat and we built it back up with 3 coats of barrier coat and three coats of epoxy prior to the AF.

A 40' boat would be about $400 and would take less than a day.

Jeff
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Old 27-03-2017, 08:50   #7
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Re: Wet Glass Blasting through years of bottom paint

Not sure I see anything too concerning. A bit of glass fiber blushing out here and there should seal up with your epoxy barrier coat right?
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Old 27-03-2017, 08:59   #8
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Re: Wet Glass Blasting through years of bottom paint

Quote:
Originally Posted by WoodFamSkipper View Post
I am midway through having my hull bottom blasted right now to remove years of basecoat + antifoul paints on a 40' monohull

Motivation: flaking, wide range of crumbling down to all different layers including the thin red gelcoat topper
Surveyor recommended stripping to gelcoat and brining back up with 2 basecoats and 2 AF coats

As an ex-charter boat, it's layers are like a gobstopper:
Gel coat
Super thin red paint - well bonded to gel
Grey base
Blue AF
More grey base
More blue
Strange green gloss plasticky coat in parts
More blue

I tried scraping, some came off thick and fast, some stuck way better and progress was not quick enough

I tried Interlux 299e fibreglass friendly stripper. I think I join the disappointed side of users, with too much paint layers for it to be able to assist

I waved white flag and consulted blasters.
Paint is coming off good now, but I am at the other end of the spectrum.

I am now concerned that it's taking too much off of the boat

I have found spots where it has been blasted for too long and gone past white and found fibreglass
(Worst case at this point is not knowing how thin the fibre could/would get before being a risky weak spot)

Questions:
How do I cover up the gelcoat-less spots?
Would a roughed up gelcoat layer be a good blank canvas to paint directly on to with base coat paint?
I've heard and seen mention of "fairing" but don't fully understand the technique, or when to apply it - do I have to prep/prime the roughened gelcoat before painting on the first coat of "Interlux Interprotect 2000 base"?
I do get that topside repairs and detailing want to be done with extra care to ensure a good appearance and finish - is bottom painting and prep simpler? To achieve solid protection instead of aesthetics?

Can of worms currently open - want to close and seal it safely, rather than saran-wrap it and naively drop it into the water
I'm wondering if the blasting that got into glass didn't uncover blisters which needed attention anyway?
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Old 27-03-2017, 10:10   #9
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Re: Wet Glass Blasting through years of bottom paint

Quote:
Originally Posted by Mikado View Post
I'm not sure of where you are located, but in Central Florida there is a company called Bottom Savers. He uses a patented type of planing tool to remove paint, epoxy, barrier coat, even gel coat. He can stay within about .003" tolerance. He took my boat bottom down to gel coat and we built it back up with 3 coats of barrier coat and three coats of epoxy prior to the AF.

A 40' boat would be about $400 and would take less than a day.

Jeff
Correction.......He took the bottom down to bare fiberglass then we built it back up as described.
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Old 27-03-2017, 10:13   #10
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Re: Wet Glass Blasting through years of bottom paint

Hi Jeff, lookef around and can't find "bottom savers" do you have any contact info?
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Old 27-03-2017, 10:22   #11
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Re: Wet Glass Blasting through years of bottom paint

Quote:
Originally Posted by SeaWings 38 View Post
Hi Jeff, lookef around and can't find "bottom savers" do you have any contact info?
Sorry, company name is Boat Savers.

This is the contact info that I have:

Boat Savers
1 Banton Pl
Palm Coast, FL 32137

Contact: Thomas Musto
Title: Owner
Phone: 386-235-1154
tmusto7@hotmail.com
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Old 28-03-2017, 14:47   #12
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Re: Wet Glass Blasting through years of bottom paint

I am just about to start the same project and a friend suggested soda blasting. This is meant to be a lot kinder to the gel coat. Had anybody heard of this and does it work
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Old 28-03-2017, 20:00   #13
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Re: Wet Glass Blasting through years of bottom paint

Quote:
Originally Posted by sailu2 View Post
I am just about to start the same project and a friend suggested soda blasting. This is meant to be a lot kinder to the gel coat. Had anybody heard of this and does it work


If I could rewind a week back, I would of gone for soda-blasting instead of wet glass . The job is now complete and I think that it was too abrasive on the gelcoat. I have some bad edges left too, which means I have to build the gelcoat back up and buff finish to a shine. Can't cover it up with bottom paint.

Blasting uncovered a lot of air bubbles in the gel coat too - need to fill them in.
Due to loss of density of gelcoat too, a guy recommended that I do an extra basecoat or two to be safe
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Old 28-03-2017, 20:19   #14
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Re: Wet Glass Blasting through years of bottom paint

Quote:
Originally Posted by WoodFamSkipper View Post
If I could rewind a week back, I would of gone for soda-blasting instead of wet glass . The job is now complete and I think that it was too abrasive on the gelcoat. I have some bad edges left too, which means I have to build the gelcoat back up and buff finish to a shine. Can't cover it up with bottom paint.

Blasting uncovered a lot of air bubbles in the gel coat too - need to fill them in.
Due to loss of density of gelcoat too, a guy recommended that I do an extra basecoat or two to be safe
I'm pretty sure what you are calling air bubbles in the gelcoat are in fact blisters. You need to ensure that all the blistered areas are completely dry prior to any painting. This can take weeks depending upon the weather. I would recommend picking up a moisture meter and going over the entire bottom thoroughly. The time to do blister/moisture repair is now while you have it all stripped down.

Prior to bottom paint you should consider discussing with a professional the proper steps to restore the bottom. This might include re-bedding the thru hulls and barrier/epoxy coats prior to bottom paint.

Good luck!

Jeff
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Old 29-03-2017, 01:18   #15
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Re: Wet Glass Blasting through years of bottom paint

They told me 2 paints of basic coat in bi-component epoxy, and one more mono-component epoxy, different color, for better working in the next AF cycle.

As all boats tend to stay for long...a hard finish is preferable

I try to entrust a reseller of a producer of choice, no chandler

BTW..
Web sites of producers are awfully simplistic and unhelpful...a shame.
No boats has history of previous paint job...oh..oh..
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